Unrecognized tax benefit (Detail) - USD ($) $ in Thousands |
12 Months Ended | |
---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
|
Income Tax Disclosure [Abstract] | ||
Beginning Balance | $ 1,539 | $ 1,314 |
Increase/(Decrease) of unrecognized tax benefits taken in prior years | (126) | 6 |
Increase/(Decrease) of unrecognized tax benefits related to current year | 62 | 219 |
Ending Balance | $ 1,475 | $ 1,539 |